1. Field of the Invention
The present invention relates to a multilayer integrated substrate from which a plurality of multilayer ceramic elements are obtained, and also relates to a method of manufacturing the multilayer ceramic elements by using the multilayer integrated substrate. More specifically, the present invention relates to modifications for increasing the strength of the multilayer integrated substrate that includes breaking grooves for facilitating the process of breaking the multilayer integrated substrate to remove the multilayer ceramic elements.
2. Description of the Related Art
To increase manufacturing efficiency, multilayer ceramic elements such as multilayer ceramic substrates are often prepared in the form of a multilayer integrated substrate, and are obtained from the multilayer integrated substrate by breaking it.
FIG. 10 is a plan view schematically showing a conventional multilayer integrated substrate 1.
The multilayer integrated substrate 1 is obtained by firing a laminate of a plurality of ceramic green sheets so as to have a laminated structure that includes a plurality of ceramic layers.
The multilayer integrated substrate 1 is provided with a plurality of breaking grooves 2 arranged in the main surface in a grid pattern. Desired multilayer ceramic elements 4 are constructed in blocks 3 sectioned by the breaking grooves 3. The multilayer ceramic elements 4 can be then obtained by breaking the multilayer integrated substrate 1 along the breaking grooves 2.
With regard to electronic components mounted in, for example, mobile communication devices, reduction in their heights has been demanded. To satisfy such a demand, the heights of multilayer ceramic elements included in the electronic components must also be reduced.
Accordingly, with reference to FIG. 10, the thickness of the multilayer integrated substrate 1 must be reduced to make the multilayer ceramic elements 4 thinner.
On the other hand, processes such as plating, printing of solder paste, mounting of other electronic components, and other processes, are required for constructing the multilayer ceramic elements 4. In order for all of the multilayer ceramic elements 4 to be processed together at the same time, it is efficient to complete such processes before the multilayer ceramic elements 4 are obtained from the multilayer integrated substrate 1.
When the thickness of the multilayer integrated substrate 1 is reduced as described above, however, undesirable fracturing of the multilayer integrated substrate 1 along the breaking grooves 2 often occurs. Such undesirable fracturing is caused by, for example, pressure or heat applied to the multilayer integrated substrate 1 during the above-described processes such as mounting of components.
In extreme cases, the multilayer integrated substrate 1 may also be fractured due to nonuniform shrinkage in the firing process or thermal shock when the temperature decreases.
In order to overcome the problems described above, preferred embodiments of present invention provide a multilayer integrated substrate and a method for manufacturing multilayer ceramic elements by using the multilayer integrated substrate, which are free from the above-described problems.
Preferred embodiments of the present invention may be applied to a multilayer integrated substrate which is obtained by firing a laminate constructed of a plurality of ceramic green sheets, which has a laminated structure including a plurality of ceramic layers, and which is provided with breaking grooves arranged in the main surface in a grid pattern and multilayer ceramic elements which are constructed in a plurality of blocks sectioned by the breaking grooves and which are obtained by breaking the multilayer integrated substrate along the breaking grooves. To attain the above-described advantages, the multilayer integrated substrate of preferred embodiments of the present invention includes one or more fracture-preventing members which are disposed so as to cross at least one of the breaking grooves.
According to the multilayer integrated substrate of preferred embodiments of the present invention, the fracture-preventing members preferably include one or more fracture-preventing conductors which contain a metal component. Preferably, the fracture-preventing conductors are provided at the ends of the breaking grooves in the region closer to the periphery of the multilayer integrated substrate than the intersectional points of the breaking grooves, and each of the multilayer ceramic elements is constructed in each of the blocks that are surrounded by the breaking grooves at four sides.
The fracture-preventing conductors preferably include one or more fracture-preventing conductive films disposed on at least one of the ceramic layers.
In addition, the above-described fracture-preventing conductive films are preferably disposed on at least one of the surface boundaries in the ceramic layers.
The fracture-preventing members may be disposed in a margin of the multilayer integrated substrate. In such a case, the fracture-preventing members may be arranged so as to cross two or more of the breaking grooves that are substantially parallel to each other, or to cross two of the breaking grooves that intersect each other.
The fracture-preventing conductors may include, instead of the fracture-preventing conductive films, one or more fracture-preventing conductive via holes which are formed so as to penetrate through at least one of the ceramic layers.
In such a case, the fracture-preventing conductive via holes are preferably formed so as to penetrate through one or more of the ceramic layers in which the plurality of breaking grooves are not provided.
Preferably, the fracture-preventing conductors are formed by being fired together with the laminate at the same time. In addition, the fracture-preventing conductors preferably contain substantially the same ceramic component as a ceramic component contained in the ceramic layers.
Other preferred embodiments of the present invention provide a method of manufacturing multilayer ceramic elements by using the above-described multilayer integrated substrate. The manufacturing method for multilayer ceramic elements of these preferred embodiments of the present invention include the steps of preparing the multilayer integrated substrate constructed as described above, and breaking the multilayer integrated substrate along the breaking grooves.
The manufacturing method for multilayer ceramic elements may further include the step of mounting electronic components on the blocks provided in the multilayer integrated substrate.
According to preferred embodiments of the present invention, the multilayer integrated substrate is provided with fracture-preventing members arranged to cross the breaking grooves, so that the strength thereof is increased. When the fracture-preventing conductors containing a metal component are used as the fracture-preventing members, undesirable fracturing of the multilayer integrated substrate along the breaking grooves is efficiently prevented due to ductility of the metal component.
More specifically, fracturing of the multilayer integrated substrate before the multilayer ceramic elements are obtained therefrom is prevented during the various processes applied to the multilayer integrated substrate.
Since fracturing does not easily occur, the dimensions of the multilayer integrated substrate may be increased. Accordingly, the number of multilayer ceramic elements constructed on the multilayer integrated substrate may also be increased. As a result, the manufacturing cost of the multilayer ceramic elements is greatly reduced.
Easiness of breaking the multilayer integrated substrate along the breaking grooves may be controlled by adjusting the depth and the shape of the breaking grooves. In addition, the strength of reinforcement to prevent undesirable fracturing may be controlled by the fracture-preventing conductors. Accordingly, processing conditions for the various processes applied to the multilayer integrated substrate may more freely be set, so that the manufacturing efficiency of the multilayer ceramic elements is increased.
As described above, the fracture-preventing conductors may be disposed so as to cross the breaking grooves at the ends thereof and in the region closer to the periphery of the multilayer integrated substrate than the intersectional points of the grooves, and the multilayer ceramic elements may respectively be constructed in the blocks surrounded by the breaking grooves at four sides. In such a case, the fracture-preventing conductors may be formed without affecting the regions in which the multilayer ceramic elements are constructed.
In addition, when the fracture-preventing conductive films are provided to define the fracture-preventing conductors, the effect of reinforcement for preventing undesirable fracturing may be applied to a relatively large area.
In addition, when the fracture-preventing conductive films are provided on at least one of the surface boundaries in the ceramic layers, the fracture-preventing conductive films are not divided by the breaking grooves.
In addition, when the fracture-preventing members are disposed at the margin of the multilayer integrated substrate, the layout of the multilayer ceramic elements may be determined without considering the fracture-preventing conductive members. Accordingly, the multilayer ceramic elements may be constructed and arranged to cover a relatively large area.
As described above, the fracture-preventing members disposed at the margin as described above may be formed so as to cross the breaking grooves that are substantially parallel to each other. In such a case, the effect of reinforcement for preventing undesirable fracturing may be provided over a relatively wide area along the sides of the multilayer integrated substrate.
In addition, the fracture-preventing members may also be arranged so as to cross breaking grooves that intersect each other. In such a case, undesirable fracturing of the multilayer integrated substrate at the corner thereof is effectively prevented.
In addition, when the fracture-preventing conductive via holes are provided to define the fracture-preventing conductor, the vertical dimensions may easily be increased compared to the above-described fracture-preventing conductive films. Accordingly, the effect of reinforcement is greatly improved. Especially when the fracture-preventing conductive via holes are formed so as to penetrate through more than one of the ceramic layers, the vertical dimensions of the fracture-preventing conductive via holes are further increased, so that the effect of the reinforcement is even more improved.
In addition, when the fracture-preventing conductive via holes are formed so as to penetrate through the ceramic layers in which the breaking grooves are not provided, the fracture-preventing conductive via holes are not divided by the breaking grooves.
In addition, the fracture-preventing conductors may be formed by being fired together with the laminate constructed of a plurality of ceramic green sheets, and the fracture-preventing conductors may contain substantially the same ceramic component as the ceramic component contained in the ceramic layers. In such a case, the fracture-preventing conductors shrink in a manner that is similar to the surrounding ceramic portions during the firing process, so that the internal stress of the multilayer integrated substrate is reduced. Accordingly, fracturing due to the internal stress is prevented, and undulation and warping of the multilayer integrated substrate are prevented from occurring.
Accordingly, the multilayer ceramic elements are manufactured at high yield by using the above-described multilayer integrated substrate.
In addition, the manufacturing process of the multilayer ceramic elements may include the step of mounting the electronic components on the blocks provided in the multilayer integrated substrate. In such a case, the conventional-type multilayer integrated substrate would easily be fractured along the breaking grooves in the step of mounting the electronic components. Such fracturing, however, is effectively prevented by using the multilayer integrated substrate of preferred embodiments of the present invention. Accordingly, the step of mounting other electronic components may be performed without any problems.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the detailed description of preferred embodiments thereof with reference to the drawings.